1. Field of the Invention
The present invention relates in general to an LED lamp, and more particularly to an LED lamp tube.
2. Description of the Related Art
Fluorescent lamps are a common type of illuminating lamps people use, but at present LED lamps have been gradually replacing the conventional fluorescent lamps and becoming the main stream in the market, due to the advantages including environment friendly, energy conservation, longer lifespan, and higher efficiency.
Due to their structural characteristics, as well as in consideration of their relatively high heat production, at present the LED lamp tubes on the market usually have a common structure, in which a circuit board with a plurality of LED units is disposed inside a tube body, and connectors mounted at the two ends of the tube body are plugged into a standardized fluorescent tube fixture for fixing the tube and obtaining electrical power, the heat generated by the LED units is first conducted to the tube body through the circuit board and dissipated to the air finally. Wherein the tube body is required to play a triple role: light directing, circuit board fixing and heat dissipating, in different ways to satisfy these requirements, the tube bodies of the existing LED lamp tubes could be divided into two types: one is made of plastic tube, its front side is transparent for light and the LED circuit board is mounted inside, the light goes through the front transparent side whilst the heat generated by the LED units is conducted from the circuit board to the tube body and eventually dissipated into the air; another one includes a plastic tube and an extra aluminum heat sink mounted on the back side of the tube, the light goes through the front transparent side whilst the heat generated by the LED units is conducted from the circuit board to the aluminum heat sink and eventually dissipated into the air, whereby an enhanced heat dissipation is obtained.
The two connectors at the ends of the tube are used to fix the LED lamp tube in a lamp fixture, thereby obtaining electrical power, as an LED lamp tube in place is usually horizontally placed, wherein only the two ends of the LED lamp tube are fixed and supported, the middle portion of the LED tube suffers from a downwards stress due to gravity. Under such a circumstance, for the first type of LED tube, as the plastic material will soften gradually by heat, as well as influenced by the action of gravity, the middle of the LED lamp tube will gradually deform and then to be obviously deflexed after a long period of use, the aesthetics and safety of the LED lamp tube are so impaired. For the second type of the LED tubes, as beneficiated from the supporting by the aluminum heat sink mounted on the back side, besides the better heat dissipation, the LED lamp tube will not deform easily by heat, and therefore could remain in aesthetic for a long period and has a more stable fixing. However, as using aluminum materials, the manufacturing cost is significantly increased and its market competence is so impaired. Furthermore, as fixed by the aluminum heat sink, the LED circuit is disposed more closely to the front side of the tube, the emitting angle is reduced and the lighting effect is consequently impaired.
As described above, the LED lamp tube is fixed and powered by the connectors being engaged with the lamp fixture, the metal pins mounted on the connectors of LED tube so have to be assembled accurately to engage with the holders, as well as to have adequate strength to ensure a firm fixation, and no rotation or displacement occurred when a torsional force or other external forces is applied. An existing method for that is to use adhesive to adhere the connectors to the ends of the tube, but with this method, the connectors are not removable once adhered, unless ruining the connection. Moreover, the heat generated during the operation of the LED lamp tube, would soften the adhesives, the connection may come loose under the action of gravity or other external forces after a long period of use.
In addition to above, usually a LED lamp tube is powered by an DC power converted from AC mains, but AC mains may be unstable in frequency in some cases, thereby influencing the value of the current passing through the LED units, the excessive current may lead to permanent luminous decay of the LEDs, consequently permanently degrades brightness of the LED lamp tube.